I watched this movie about peak oil, and couldn't stop thinking about the sustainability of farmland in the North West. found this washington harvest calendar.
I would like to inject some real world experience into this otherwise abstract discussion of food and permaculture.
In addition to being an ecological biologist, a permaculture production food farmer for 9 years, and an expert on biomass fuels, I have also been teaching permaculture since 1997 and have worked in many countries on food/energy production design issues. I have certified more than 400 people in permaculture design since 1997. For more info on this see my site at www.permaculture.com
So in light of my experience I have a couple of things to say. Let us dispense, for the moment only, with the talk of hunter-gatherer models since, to return to that state or to imitate it with design would meet limited acceptance. This is not the core design goal of permaculture although some of our small scale subsistence agriculture designs vaguely look like a hunter-gatherer paradise (i.e. it never existed like this in nature.) The issue of private property as we now define it also complicates that model. We are living in an agricultural age and permaculture offers huge benefits to both production and subsistence agriculture.
As far as I know I was one of the only farmers fully utilizing permaculture to produce surplus food for sale in the US as a full time occupation. On approximately two acres-- half of which was on a terraced 35 degree slope--I produced enough food to feed more than 300 people (with a peak of 450 people at one point), 49 weeks a year in my fully organic CSA on the edge of Silicon Valley . If I could do it there you can do it anywhere.
I did this for almost nine years until I lost the lease to my rented land. My yields were often 8 times what the USDA claims are possible per square foot. My soil fertility increased dramatically each year so I was not achieving my yields by mining my soil. On the contrary I built my soil from cement-hard adobe clay to its impressive state from scratch. By the end I was at over 22% organic matter with a cation exchange capacity (CEC) of over 25. CEC is an indirect measure of soil humus or the ability of the soil to hold nutrients available to crops. The higher the number the more nutrients are stored and available. For reference, most Class I commercial agricultural soil is lucky to hit 2% organic matter--the dividing line between a living and dead soil--with a CEC around 5.
At most times I had no more than half of my land under production with the rest in various stages of cover cropping. And I was only producing at a fraction of what would have been possible if I had owned the land and could have justified the investment into an overstory of integrated tree, berry, flower and nut crops along with the various vegetable and fruit crops. The farm produced so much income that I was routinely in the top 15% of organic farms in California (which has over 2000 organic farms) in most years on a fraction of the land that my colleagues were using. I grew over 45 different kinds of crops so my financial success cannot be attributed to growing a few high value crops like Yuppie Chow (salad mix).
Unlike other organic farmers, I almost never used even organic pesticides on my farm. The permaculture ecosystem I designed was so self-managing and self-maintaining with natural controls such as carnivorous insects, toads, lizards, snakes, owls, bats, and other allies, that it was rare that I needed to intervene (I can count the times on one hand that I intervened over 9 years). On the few occasions I did, I used coffee solution made from waste caf é coffee. You didn't think plants made caffeine to get you high did you? Caffeine is an extremely effective natural insecticide, which degrades in the sunlight or air in about 24 hours after use.
On the subsistence agriculture level, we permies regularly have designed productions systems around the world, which feed everyone living in a given house within a 50-foot radius of the house. This rule of thumb holds pretty well because the more folks who live there, the bigger the house, the larger the surface area, so no more than 50 feet is really necessary.
The math is easy. With a polyculture, yields of 3-10 pounds of food per square foot are easy to come up with in most climates. For comparison, commercial agriculture in California , which is way inefficient, routinely runs about 1.5-2.5 pounds per square foot per year across a wide variety of crops. People need to eat about two pounds of mixed food a day if active, or around 750 pounds a year. In a good but somewhat sloppy design, you need about 500 square feet per person MAXIMUM. In a very good design, 200 square feet will do the job. If your diet is heavy on grain you'll need more space but not an astronomical amount. Utilize a greenhouse to extend seasons and exchange air rich in carbon dioxide from chicken houses or human houses, which otherwise would go to waste, and yields ratchet up even more. Take a little more space and include ducks and aquaculture into the mix and the yields become quite diverse and substantial. This sort of system is typical in Vietnam now and there is no longer any measurable hunger there. Wouldn't it be nice if the US could do that with its "superior" first world agricultural system?
Can't do this on a commercial scale? Tell that to Archer Daniels Midland who operates many acres of greenhouses in Decatur using partially integrated production of fish, lettuce and other vegetables using waste carbon dioxide, grain by-products and other by-products from its 100-million gallon per year alcohol fuel production facility, while delivering these profitable agricultural products in trucks running on biodiesel (made from the corn and soybeans they process). This qualifies as commercial scale, very rudimentary permaculture that is wildly profitable and productive.
As a reality check, I'd like to remind everyone that in the 1850's, prior to refrigerated transport, New York City supplied all its food for a population of over a million from within 7 miles of the borders of the city. (It wasn't worth the cost of horse feed and time to go further than 7 miles to export food into the city). No one would discount a system of community food security for one million people as non-commercial.
There are two main reasons known for the dramatically increased productivity of a polyculture—the benefit of mycorhyzzal symbiosis (which is destroyed in chemical agriculture) and less solar saturation. Solar saturation is the point at which a plants' photosynthetic machinery is overwhelmed by excess sunlight and shut down. In practice, this means that most of our crop plants stop growing at about 10am and don't start again until about 4 in the afternoon. Various members of a polyculture shade each other, preventing solar saturation, so plants metabolize all day. Polyculture as we pursue in permaculture uses close to 100% of the sunlight falling on its mixed crops. Monoculture rarely can use more than 30% of the total sunlight received before saturation. How long could you run any business without external support at 30% efficiency? When you look at a simple Mexican permaculture example, growth of the three sisters of corn, beans and squash (not even counting the 200 vegetables of various sorts growing in the shade of the sisters) you get close to 90% solar efficiency. When you total up the pounds of food from a Mexican acre you get FAR MORE FOOD than the highest yielding nitrogen soaked Iowa cornfield. This is the myth of the green revolution; that the highest total food yields occur in chemical monoculture.
Enough of this. The argument that we don't have enough food to go around is specious anyway. We currently produce more than twice the amount of food we need to feed everyone, even with the extremely inefficient model of monoculture. What starving people lack is money to buy food which is not considered a right but a commodity. Even being able to buy the food isn't a guarantee of access. Midwesterners find it cheaper to burn 5 cent a pound corn in stoves for heat even though Mexican families are willing to pay up to $1 a pound for corn to feed their family.
So you say, "Well if you're such a wiseguy and you obviously would make so much more money from the greater yields of a simple three crop permaculture system, why don't corporations in the Midwest do it to make more money?" This gets to the core of the problemw--hich is not population/resources and/or biological models of overpopulation which typically apply to wild animals.
Capitalism is concerned with more than just making money. The reason why monocultures are favored by corporations EVEN THOUGH THEY ARE THE LEAST EFFICIENT WAY OF PRODUCING FOOD in pounds of food per acre is that it can be done with the least amount of labor. To harvest the three sisters you would need a digital harvester--i.e. two hands--not a combine. Even though the increased labor would be totally justified by the increased profit, corporations are totally allergic to dealing with labor. Labor is messy. It organizes, it wants a fair share of the profit, cities want tax money to pay for worker habitat infrastructure and other pesky things that corporations will avoid at all costs. Our current form of agribusiness is a textbook case of design maximizing the advantage of capital to the disadvantage of labor facilitated by the artificially low cost of energy.
The other reason is control of the market. It is now estimated that 80 percent of the world's arable (read European-style plowed) agricultural land is now in the hands of multi-nationals. It has served their needs to keep productivity low to make it possible to get a hold of as much of the means of production as possible. Farmers who are barely making a living sell their land for a fraction of those making a good profit. Midwest corn farmers generally net only about $50-75 per acre on corn on a gross income of $300 per acre.
My discussion above is not to be taken as a suggestion that population growth is not a problem, it is. So let me make a quick comment on population, from a designer's point of view, which is totally related to the structural issues above. I dare anyone to find an example in which population is stable yet there is no system for security in old age. It has been shown in countless studies that the ONLY consistent reason why population stabilizes is that people know they will have security in their old age. At that point they stop having excess children. Why? It has absolutely nothing to do with the biological resource-population relationships. We are not wild animals and have markedly different behavior. In a developing country, or any country for that matter, without a secure social security system for the aged, you need at least two kids to support each elderly adult. In virtually every case studied where stabilization of social systems occurred, women immediately find systems to end unwanted pregnancy. Herbal indigenous methods for ending fertility are known all over the world. In my own Italian heritage--hardly a herb-oriented aboriginal tribe, even into the 1900's, utilized ergot obtained from the local apothecary to end unwanted pregnancy.
So structural adjustment--the neoliberal formula the World Bank and IMF impose on the developing world--ensures population growth. By intentionally eliminating a secure social safety net as a condition of borrowing money, population growth--and therefore market growth for various consumer goods--continues to grow. Therein lies the rub. If population doesn't continue to grow, capitalists rapidly run out of customers. Can't let that happen now can we?
Permaculture design offers an alternative security for old age when the family has even a little land. In the Deccan desert of India , where there is huge success with permaculture turning hundreds of square miles of man-made desert back into productive designed rain forest, there is a saying: "Trees are better than sons". Sons might take care of you in your old age but income or trade from your productive trees (food, timber and fuel) definitely will. This approach offers families security to limit population growth and takes the supply of old age security back into the people's hands.
Restorative agriculture—which goes far beyond sustainable agriculture--depends on solar energy replacing fossil fuel use. Buckminster Fuller and I discussed this back in 1983 when he wrote the foreword for my book Alcohol Can Be A Gas!, which accompanied my ten part PBS television series at that time. (Alcohol is a virtually pollution free engine fuel which is superior in almost every way to gasoline.) World photosynthesis in its fully undesigned state, produces biomass in wasteful agriculture and in the wild which far exceeds human need. Our analysis shows that world biomass photosynthesis produces between 6 and 15 times what we used to power every human need every year, including food, electricity, transportation, and heat.
In a designed system, especially a permaculturally-designed system, we could increase the biomass produced by an order of magnitude and in so doing supply all our needs in a much smaller footprint. For instance, you only get about 200 gallons per acre of alcohol fuel from corn, but 1000 gallons from sugar beets, 1200 from Jerusalem Artichokes, 1500 gallons from annual sugar cane in southern states and a variety of other crops which, when properly designed for climate, might yield 2500 gallons per year from two crop cycles. This would be done while increasing soil fertility and providing all the animal food we need as a by-product (replacing the corn which largely goes for animal feed now) at a fraction of the energy cost of corn-soybean agribusiness. This is all possible right now without any new technology.
The Department of Energy-sponsored program to reduce the cost of cellulose-dissolving enzymes. Soon, yields based on that carbohydrate (cellulose) rather than the relatively scarce starch or sugar carbohydrate scenarios described above will ratchet up cost-effective yield another order of magnitude. (We could do it right now with current technology but the fuel would be about $1.65/gallon wholesale). Once again this is just scratching the surface.
I could go on for two weeks non-stop about this—my colleagues and I do so in my permaculture design courses. The point is that although humans are great at creating deserts and poverty, we also have the incredible capacity to design ecological systems that work for everyone--even some corporations. The argument that we can't produce enough ecologically is, at its source, promoted by corporations who benefit from a view of scarcity and limited resources which they control. Their constant cry is TINA "There Is No Alternative". Right, and the wizard says, "Pay no attention to the man behind the curtain!"
Around the world people are demonstrating that, not only are there alternatives, there are alternatives that allow us all to take care of each other and the rest of the species we live with, and to direct surpluses from our designs back to this care. These are the three main tenets of Permaculture design. We aren't waiting for governments, corporations, or bureaucracies to solve the world's problems. We will do it with or without their help. We are already doing it and no one can stop us because we can't be forced to buy what we don't need anymore. Since few of us in permaculture education are hired by anyone in business or government, we can't be fired or threatened.
I like to say, if you want to end transnational capitalism, (the very opposite of bioregionalism), then stop giving them your capital. To do that you need to start producing what you need--plus some surplus for others--bioregionally and I would respectfully suggest that permaculture design is a good tool to begin that process.
the other thing i want to add is that the model Blume is talking about is based on the efficiency of having production be within 50 feet of the front door of each person. as you increase distance you exponentionately (excuse my spelling) decrease efficiency. packing in tons of people onto a peice of land will change a lot of things for your design.
high-density settlement design is a little different then production design.
so, this is really rough but i estimate a household living in a house about 25x25 will need to be on a property somewhere around 125 x 100 feet or 12,500 square feet.
1 acre = 43 560 square feet
which would mean around 3 households per acre in terms of use of space rather then . how many people in each household? depends on your design.
if we take destons 346 people per acre per year, then we have each household feeding 115 people per year. or we could also produce fiber and medicine and fuel and direct more of that production towards systems that reduce work.
How much land is required to support a person's existence so they can eat for a year, make enough food to sell to others to pay for the food and living expenses and medicine and entertainment and home repairs and multiply per person?
John Jeavons, of Grow Bio Intensive, estimates 1000 square feet per person for calorie needs but 4000 for sustainable farming, as you need room for compost, and to leave half the land wild. This requires intensive cultivation, with composting, double digging, close planting, rotation, etc.
I would like to inject some real world experience into this otherwise abstract discussion of food and permaculture.
In addition to being an ecological biologist, a permaculture production food farmer for 9 years, and an expert on biomass fuels, I have also been teaching permaculture since 1997 and have worked in many countries on food/energy production design issues. I have certified more than 400 people in permaculture design since 1997. For more info on this see my site at www.permaculture.com
So in light of my experience I have a couple of things to say. Let us dispense, for the moment only, with the talk of hunter-gatherer models since, to return to that state or to imitate it with design would meet limited acceptance. This is not the core design goal of permaculture although some of our small scale subsistence agriculture designs vaguely look like a hunter-gatherer paradise (i.e. it never existed like this in nature.) The issue of private property as we now define it also complicates that model. We are living in an agricultural age and permaculture offers huge benefits to both production and subsistence agriculture.
As far as I know I was one of the only farmers fully utilizing permaculture to produce surplus food for sale in the US as a full time occupation. On approximately two acres-- half of which was on a terraced 35 degree slope--I produced enough food to feed more than 300 people (with a peak of 450 people at one point), 49 weeks a year in my fully organic CSA on the edge of Silicon Valley . If I could do it there you can do it anywhere.
I did this for almost nine years until I lost the lease to my rented land. My yields were often 8 times what the USDA claims are possible per square foot. My soil fertility increased dramatically each year so I was not achieving my yields by mining my soil. On the contrary I built my soil from cement-hard adobe clay to its impressive state from scratch. By the end I was at over 22% organic matter with a cation exchange capacity (CEC) of over 25. CEC is an indirect measure of soil humus or the ability of the soil to hold nutrients available to crops. The higher the number the more nutrients are stored and available. For reference, most Class I commercial agricultural soil is lucky to hit 2% organic matter--the dividing line between a living and dead soil--with a CEC around 5.
At most times I had no more than half of my land under production with the rest in various stages of cover cropping. And I was only producing at a fraction of what would have been possible if I had owned the land and could have justified the investment into an overstory of integrated tree, berry, flower and nut crops along with the various vegetable and fruit crops. The farm produced so much income that I was routinely in the top 15% of organic farms in California (which has over 2000 organic farms) in most years on a fraction of the land that my colleagues were using. I grew over 45 different kinds of crops so my financial success cannot be attributed to growing a few high value crops like Yuppie Chow (salad mix).
Unlike other organic farmers, I almost never used even organic pesticides on my farm. The permaculture ecosystem I designed was so self-managing and self-maintaining with natural controls such as carnivorous insects, toads, lizards, snakes, owls, bats, and other allies, that it was rare that I needed to intervene (I can count the times on one hand that I intervened over 9 years). On the few occasions I did, I used coffee solution made from waste caf é coffee. You didn't think plants made caffeine to get you high did you? Caffeine is an extremely effective natural insecticide, which degrades in the sunlight or air in about 24 hours after use.
On the subsistence agriculture level, we permies regularly have designed productions systems around the world, which feed everyone living in a given house within a 50-foot radius of the house. This rule of thumb holds pretty well because the more folks who live there, the bigger the house, the larger the surface area, so no more than 50 feet is really necessary.
The math is easy. With a polyculture, yields of 3-10 pounds of food per square foot are easy to come up with in most climates. For comparison, commercial agriculture in California , which is way inefficient, routinely runs about 1.5-2.5 pounds per square foot per year across a wide variety of crops. People need to eat about two pounds of mixed food a day if active, or around 750 pounds a year. In a good but somewhat sloppy design, you need about 500 square feet per person MAXIMUM. In a very good design, 200 square feet will do the job. If your diet is heavy on grain you'll need more space but not an astronomical amount. Utilize a greenhouse to extend seasons and exchange air rich in carbon dioxide from chicken houses or human houses, which otherwise would go to waste, and yields ratchet up even more. Take a little more space and include ducks and aquaculture into the mix and the yields become quite diverse and substantial. This sort of system is typical in Vietnam now and there is no longer any measurable hunger there. Wouldn't it be nice if the US could do that with its "superior" first world agricultural system?
Can't do this on a commercial scale? Tell that to Archer Daniels Midland who operates many acres of greenhouses in Decatur using partially integrated production of fish, lettuce and other vegetables using waste carbon dioxide, grain by-products and other by-products from its 100-million gallon per year alcohol fuel production facility, while delivering these profitable agricultural products in trucks running on biodiesel (made from the corn and soybeans they process). This qualifies as commercial scale, very rudimentary permaculture that is wildly profitable and productive.
As a reality check, I'd like to remind everyone that in the 1850's, prior to refrigerated transport, New York City supplied all its food for a population of over a million from within 7 miles of the borders of the city. (It wasn't worth the cost of horse feed and time to go further than 7 miles to export food into the city). No one would discount a system of community food security for one million people as non-commercial.
There are two main reasons known for the dramatically increased productivity of a polyculture—the benefit of mycorhyzzal symbiosis (which is destroyed in chemical agriculture) and less solar saturation. Solar saturation is the point at which a plants' photosynthetic machinery is overwhelmed by excess sunlight and shut down. In practice, this means that most of our crop plants stop growing at about 10am and don't start again until about 4 in the afternoon. Various members of a polyculture shade each other, preventing solar saturation, so plants metabolize all day. Polyculture as we pursue in permaculture uses close to 100% of the sunlight falling on its mixed crops. Monoculture rarely can use more than 30% of the total sunlight received before saturation. How long could you run any business without external support at 30% efficiency? When you look at a simple Mexican permaculture example, growth of the three sisters of corn, beans and squash (not even counting the 200 vegetables of various sorts growing in the shade of the sisters) you get close to 90% solar efficiency. When you total up the pounds of food from a Mexican acre you get FAR MORE FOOD than the highest yielding nitrogen soaked Iowa cornfield. This is the myth of the green revolution; that the highest total food yields occur in chemical monoculture.
Enough of this. The argument that we don't have enough food to go around is specious anyway. We currently produce more than twice the amount of food we need to feed everyone, even with the extremely inefficient model of monoculture. What starving people lack is money to buy food which is not considered a right but a commodity. Even being able to buy the food isn't a guarantee of access. Midwesterners find it cheaper to burn 5 cent a pound corn in stoves for heat even though Mexican families are willing to pay up to $1 a pound for corn to feed their family.
So you say, "Well if you're such a wiseguy and you obviously would make so much more money from the greater yields of a simple three crop permaculture system, why don't corporations in the Midwest do it to make more money?" This gets to the core of the problemw--hich is not population/resources and/or biological models of overpopulation which typically apply to wild animals.
Capitalism is concerned with more than just making money. The reason why monocultures are favored by corporations EVEN THOUGH THEY ARE THE LEAST EFFICIENT WAY OF PRODUCING FOOD in pounds of food per acre is that it can be done with the least amount of labor. To harvest the three sisters you would need a digital harvester--i.e. two hands--not a combine. Even though the increased labor would be totally justified by the increased profit, corporations are totally allergic to dealing with labor. Labor is messy. It organizes, it wants a fair share of the profit, cities want tax money to pay for worker habitat infrastructure and other pesky things that corporations will avoid at all costs. Our current form of agribusiness is a textbook case of design maximizing the advantage of capital to the disadvantage of labor facilitated by the artificially low cost of energy.
The other reason is control of the market. It is now estimated that 80 percent of the world's arable (read European-style plowed) agricultural land is now in the hands of multi-nationals. It has served their needs to keep productivity low to make it possible to get a hold of as much of the means of production as possible. Farmers who are barely making a living sell their land for a fraction of those making a good profit. Midwest corn farmers generally net only about $50-75 per acre on corn on a gross income of $300 per acre.
My discussion above is not to be taken as a suggestion that population growth is not a problem, it is. So let me make a quick comment on population, from a designer's point of view, which is totally related to the structural issues above. I dare anyone to find an example in which population is stable yet there is no system for security in old age. It has been shown in countless studies that the ONLY consistent reason why population stabilizes is that people know they will have security in their old age. At that point they stop having excess children. Why? It has absolutely nothing to do with the biological resource-population relationships. We are not wild animals and have markedly different behavior. In a developing country, or any country for that matter, without a secure social security system for the aged, you need at least two kids to support each elderly adult. In virtually every case studied where stabilization of social systems occurred, women immediately find systems to end unwanted pregnancy. Herbal indigenous methods for ending fertility are known all over the world. In my own Italian heritage--hardly a herb-oriented aboriginal tribe, even into the 1900's, utilized ergot obtained from the local apothecary to end unwanted pregnancy.
So structural adjustment--the neoliberal formula the World Bank and IMF impose on the developing world--ensures population growth. By intentionally eliminating a secure social safety net as a condition of borrowing money, population growth--and therefore market growth for various consumer goods--continues to grow. Therein lies the rub. If population doesn't continue to grow, capitalists rapidly run out of customers. Can't let that happen now can we?
Permaculture design offers an alternative security for old age when the family has even a little land. In the Deccan desert of India , where there is huge success with permaculture turning hundreds of square miles of man-made desert back into productive designed rain forest, there is a saying: "Trees are better than sons". Sons might take care of you in your old age but income or trade from your productive trees (food, timber and fuel) definitely will. This approach offers families security to limit population growth and takes the supply of old age security back into the people's hands.
Restorative agriculture—which goes far beyond sustainable agriculture--depends on solar energy replacing fossil fuel use. Buckminster Fuller and I discussed this back in 1983 when he wrote the foreword for my book Alcohol Can Be A Gas!, which accompanied my ten part PBS television series at that time. (Alcohol is a virtually pollution free engine fuel which is superior in almost every way to gasoline.) World photosynthesis in its fully undesigned state, produces biomass in wasteful agriculture and in the wild which far exceeds human need. Our analysis shows that world biomass photosynthesis produces between 6 and 15 times what we used to power every human need every year, including food, electricity, transportation, and heat.
In a designed system, especially a permaculturally-designed system, we could increase the biomass produced by an order of magnitude and in so doing supply all our needs in a much smaller footprint. For instance, you only get about 200 gallons per acre of alcohol fuel from corn, but 1000 gallons from sugar beets, 1200 from Jerusalem Artichokes, 1500 gallons from annual sugar cane in southern states and a variety of other crops which, when properly designed for climate, might yield 2500 gallons per year from two crop cycles. This would be done while increasing soil fertility and providing all the animal food we need as a by-product (replacing the corn which largely goes for animal feed now) at a fraction of the energy cost of corn-soybean agribusiness. This is all possible right now without any new technology.
The Department of Energy-sponsored program to reduce the cost of cellulose-dissolving enzymes. Soon, yields based on that carbohydrate (cellulose) rather than the relatively scarce starch or sugar carbohydrate scenarios described above will ratchet up cost-effective yield another order of magnitude. (We could do it right now with current technology but the fuel would be about $1.65/gallon wholesale). Once again this is just scratching the surface.
I could go on for two weeks non-stop about this—my colleagues and I do so in my permaculture design courses. The point is that although humans are great at creating deserts and poverty, we also have the incredible capacity to design ecological systems that work for everyone--even some corporations. The argument that we can't produce enough ecologically is, at its source, promoted by corporations who benefit from a view of scarcity and limited resources which they control. Their constant cry is TINA "There Is No Alternative". Right, and the wizard says, "Pay no attention to the man behind the curtain!"
Around the world people are demonstrating that, not only are there alternatives, there are alternatives that allow us all to take care of each other and the rest of the species we live with, and to direct surpluses from our designs back to this care. These are the three main tenets of Permaculture design. We aren't waiting for governments, corporations, or bureaucracies to solve the world's problems. We will do it with or without their help. We are already doing it and no one can stop us because we can't be forced to buy what we don't need anymore. Since few of us in permaculture education are hired by anyone in business or government, we can't be fired or threatened.
I like to say, if you want to end transnational capitalism, (the very opposite of bioregionalism), then stop giving them your capital. To do that you need to start producing what you need--plus some surplus for others--bioregionally and I would respectfully suggest that permaculture design is a good tool to begin that process.
I think your math missed the finer points-
you must consider it was 3-10 lbs, not jst 10 lbs. so, I'll average the figure. Ill say 6.5lbs a sq. ft. across an entire acre. I find that wildly optimistic, but I have seen plots with 3-4 lbs/sf, and room for trees above... so, 6.5lb/s per square foot a year, with a human eating 2 lbs a day- or 730 lbs/year. now, we must account for 10% of the acre not producing due to paths.
So we take the sf of an acre 43264, and loose 10%, or 4326 feet=38938 feet. Times this by our optimistic food forest figure of 6.5lbs/sf=253097 lbs food. I wont calculate browse loss, which is typically 10-12%, as i am being an optimist today and will imagine that david subtracted this from his original 3-10lb statement. So, 253097 lbs of food annually divided by the 730 which a person needs annually= 346 people per acre per year, which is well within the figures he offers in his essay. Even at 10 lbs/sf an acre we come up with 533 ppl per acre. I hope this helps clear up any misconceptions about the consistency of Mr. Blumes claims.
the other thing i want to add is that the model Blume is talking about is based on the efficiency of having production be within 50 feet of the front door of each person. as you increase distance you exponentionately (excuse my spelling) decrease efficiency. packing in tons of people onto a peice of land will change a lot of things for your design.
high-density settlement design is a little different then production design.
so, this is really rough but i estimate a household living in a house about 25x25 will need to be on a property somewhere around 125 x 100 feet or 12,500 square feet.
1 acre = 43 560 square feet
which would mean around 3 households per acre in terms of use of space rather then . how many people in each household? depends on your design.
if we take destons 346 people per acre per year, then we have each household feeding 115 people per year. or we could also produce fiber and medicine and fuel and direct more of that production towards systems that reduce work.
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